In a TT bench alignment, how much should the foot be placed posterior to the midline for a SACH foot?

In transtibial (TT) bench alignment, the placement of the foot relative to the midline of the socket is crucial for achieving optimal function and stability in the prosthesis. For a SACH (Solid Ankle Cushion Heel) foot, positioning the foot posterior to the midline by 37 mm is generally recommended.

This specific alignment helps to ensure that the weight-bearing forces are appropriately distributed during gait, promoting a smooth transition from heel strike to toe-off. The 37 mm placement allows for better control during ambulation and decreases the likelihood of tippling or instability. Moreover, this distance accommodates the functionality of the SACH foot, which has a built-in compressible heel that acts as a shock absorber and provides cushioning at heel strike.

The importance of correct foot placement is critical; if the foot is positioned too far forward or backward, it can lead to gait abnormalities, increased energy expenditure, and discomfort for the user. Thus, the alignment of 37 mm behind the midline is a standard that has been established based on biomechanical principles and clinical practice for enhancing user comfort and walking efficiency.